the mathies mine experiment

On May 30, 2003, Groundhog autonomously descended into the abandoned
Mathies Mine near Pittsburgh, PA. The 1500-pound vehicle was equipped
with laser range sensors, a night vision camera, gas detectors,
sinkage sensors, and a gyroscope. 308 meters into the rapidly decaying
mine, Groundhog encountered a broken ceiling beam that draped
diagonally across the robot's path. The robot made the appropriate
decision to retreat. During the retreat the robot rebooted more than
once for some fault that is not yet clear. This was close enough to
the portal that the team intervened by communicating via a faint
wireless link. A communication loop ensued, which was cleared by our
PA DEP safety monitor who physically entered a short distance to hit a
reset button, enabeling the robot to emerge.